1. Field of the Invention
This invention relates to assembly of integrated circuits, preferably flat pack integrated circuits, to a printed circuit board. In one of its aspects, the invention relates to a completely automated method and apparatus for mounting integrated circuits on a printed circuit board wherein the integrated circuits are loaded into the apparatus as they come from the manufacturer.
2. State of the Prior Art
Printed circuit boards have up to fifty or more integrated circuits soldered thereto in a predetermined relationship. The integrated circuits have a number of leads which are formed with feet and through which the integrated circuits are soldered to the board. Prior art techniques for bonding beam-type integrated circuits to circuit boards are described in the U.S. patent to Monahan et al U.S. Pat. No. 3,793,710 (issued Feb. 26, 1974). These techniques usually involve visual alignment of the integrated circuits on the board using a microscope.
Techniques for mounting dual in-line integrated circuits to printed circuit boards are disclosed in the United States patent to Kowalski U.S. Pat. No. 3,760,484 (issued Sept. 25, 1973); Ragard et al U.S. Pat. No. 3,727,284 (issued Apr. 17, 1973); and Woodman, Jr. U.S. Pat. No. 4,063,347 (issued Dec. 20, 1977). Each of these prior art machines positions the leads of the integrated circuits through holes in the printed circuit board in an automated technique. The leads must be previously tinned and bent into proper orientation before loading into the machines.
Another prior art machine for assembling beam-type integrated circuits takes flat pack assemblies including a carrier from a single dispensing channel and removes the carrier. The integrated circuits are then moved on a rotary table to a lead-forming die by a suction means wherein the leads are bent downwardly and outwardly of the body to form pad-engaging feet. The integrated circuits are picked up by the body through suction means on the rotary table and thereafter transferred to an X-Y axis table wherein the integrated circuits are positioned in an approximate desirable location on the table. The table is programmed by a controller and moved to a predetermined location for the particular integrated circuit. However, the transfer technique is not sufficiently precise enough and the bodies of the integrated circuits vary such that precise location of the integrated circuits on the board can not be accomplished with this machine. Accordingly, an operator, who views the integrated circuit position through a microscope, must manually "jog" or move the integrated circuit to the precise location. Thereafter solder electrodes are moved into position and solder the leads to the board.
This machine requires pretinning of the leads. Thus, the integrated circuits must be removed from the carrier, tinned and then replaced in the carriers before loading into the machine. This process sometimes results in distortion of the leads and further creates an extra handling step. The positioning of the integrated circuits on the printed circuit board by the operator considerably slows down the process. Further, the operator must be careful to load the multitude of integrated circuits, typically 72 circuits, into the magazine in the precise order. Loading the magazines in the improper order can result in one or more integrated circuits mounted in improper locations on the printed circuit board.